Lubricants Containing Multifunctional Additive Packages Therein for Improving Load-Carrying Capacity, Increasing Surface Fatigue Life and Reducing Friction

ABSTRACT

The present invention provides a composition for improving load carrying capacity, extreme pressure performance, surface fatigue life, and other performance characteristics of a lubricant. The composition includes a base stock and a combination of two, three, or all of a friction modifier, and antiwear additive, an extreme pressure additive, and a surface fatigue life modifier. The present invention further provides a method for improving the performance characteristics of a lubricant. The method includes a step of mixing a lubricant with the above-described multifunctional lubricant additive composition or mixing a lubricant base stock with the above-described multifunctional lubricant additive composition.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional Application No. 60/625,416 filed Nov. 4, 2004, and is related to the following co-pending and commonly-owned applications which were filed herewith and are hereby incorporated by reference in full: “Lubricant Additive Packages for Improving Load-Carrying Capacity and Surface Fatigue Life” (Attorney Docket No. 0002290WOU, EH-11605), U.S. Ser. No. ______; “Multifunctional Lubricant Additive Package” (Attorney Docket No. 0002291WOU, EH-11679), U.S. Ser. No. ______; and “Multifunctional Lubricant Additive Package for a Rough Mechanical Component Surface” (Attorney Docket No. 0002295WOU, EH-1 1698), U.S. Ser. No. ______.

GOVERNMENT RIGHTS IN THE INVENTION

The invention was made by, or under contract with, the National Institute of Standards and Technology of the United States Government under contract number: 70NANBOH3048.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lubricant that includes a multifunctional additive composition or package for improving the performance characteristics of a lubricant. More particularly, the present invention relates to a lubricant that includes a multifunctional additive composition or package for providing a lubricant with superior performance characteristics such as improved load-carrying capacity, anti-scuffing (anti-scoring) capacity, friction reduction, and improved surface-fatigue life.

2. Description of Related Art

Mechanical systems such as manual or automatic transmissions; single and multi-speed aviation transmissions, including but not limited to those used to propel rotorcraft and those used to alter the rotational speed of sections within gas turbine engines, push-belt type continuous variable transmissions, and traction drive continuous variable transmissions, have large surface areas of contact zones. These contact portions or zones, such as drive rolling surfaces, and gear and ball-and roller bearings, are known to be susceptible to high surface pressures. In addition, internal combustion engines and other propulsion devices, especially those that are common for high-performance and racing applications, are subject to taxing demands in the form of inertial loading, high sliding and/or rolling speeds, and marginal lubrication. Moreover, the need for reducing friction, improving scuffing (scoring) resistance, and increasing surface fatigue life within larger contact zones of mechanical systems is increased by many recently developed transmission systems that are designed to be miniaturized or weight-reduced to maximize transmission throughput capacity.

To address these severe application demands, lubricants, especially those containing specific additives, play a critical role in protecting and minimizing the wear and scuffing (scoring) of surfaces. The lubricants generally reduce principal damage accumulation mechanisms of lubricated components caused by surface fatigue and overloading.

Examples of known lubricants are discussed in the following publications, which are hereby incorporated in full by reference: Phillips, W. D., Ashless phosphorus-containing lubricating oil additives, Lubricant Additives Chemistry and Application 45-111 (L. R. Rudick, Marcel Dekker, Inc. 2003); and D. Kenbeck, and T. F. Buenemann, Organic Modifiers, Lubricant Additives Chemistry and Application 203-222 (L. R. Rudick, Marcel Dekker, Inc. 2003).

Recently developed system-optimization approaches for increasing overall power throughput of mechanical systems underscore the need for new and better performing lubricant additives. By reducing friction, wear, and pressure, and improving scoring (scuffing) resistance, these additives prolong surface fatigue life for lubricated contacts within transmission systems and propulsive devices.

The present invention provides a lubricant for improving the performance characteristics of mechanical systems, such as increasing load-carrying capacity, increasing surface fatigue life and reducing friction.

SUMMARY OF THE INVENTION

The present invention provides a lubricant that includes an additive package comprising elements or components that are intended to enhance the performance characteristics of the lubricant. The additive package includes anti-wear (AW), extreme pressure (EP), friction modifying (FM), and/or surface fatigue life (SFL) modifying compositions.

In a preferred embodiment, this invention provides a lubricant having a multifunctional lubricant additive composition included therein for improving the performance characteristics of the lubricant for use in transmission fluid products that meet both civil and military specifications.

In another embodiment, the present invention provides a lubricant having a multifunctional lubricant additive composition included therein for use in improving the performance of metals and alloys of power transmission components, including gears, bearings, spines, shafts and springs.

In another embodiment, this invention provides a lubricant having a multifunctional lubricant additive composition included therein for improving the performance characteristics of engines and related propulsive devices used to power automobiles, both stock (production) and specialty (e.g. racing and other high performance) varieties, and heavy on- and off-road equipment, such as farm implements and construction equipment.

In another embodiment, the present invention provides a lubricant having a multifunctional lubricant additive composition included therein that beneficially reduces friction and scuffing (scoring), and increases resistance to surface degradation, including but not limited to fatigue, including micro- and macro-pitting, and wear.

In yet another embodiment, the present invention provides a lubricant having a multifunctional lubricant additive composition included therein for improving the performance characteristics of an applied mechanical system. Embodiments of this lubricant comprise the following components:

(a) a base stock lubricant and at least one of the (b), (c), (d) and (e) additive/modifiers described below;

(b) a friction modifying (FM) additive comprising:

-   -   (b1) a long-chain organic partial ester having the general         formula:

wherein R¹ and R² are each independently a C_(i)H_(2i+1) normal alkyl group, wherein i is an integer of about 7≦i≦15;

-   -   (b2) a short chain metallo-organic compound represented by the         general formula:

wherein X¹ is oxygen or sulfur, wherein R³ and R⁴ are each a C_(n)H_(2n+1) alkyl group, n is an integer of about 2≦n≦10, and m is an integer of about 0≦m≦4; and/or

-   -   (b3) a combination of (b1) and (b2); and/or

(c) an antiwear (AW) additive comprising:

-   -   (c1) an alkyl neutral phosphate or an aryl neutral phosphate         represented by the formula:

wherein the R⁵, R⁶, and R⁷ are each a C_(n)H_(2n+1) alkyl group of an alkyl neutral phosphate or a C₆H₅C_(m)H_(2m+1) aryl group of an aryl neutral phosphate, n is an integer of about 2≦n≦10, and m is an integer of about 0≦m≦8;

-   -   (c2) a zinc dialkyl dithiophosphate represented by the general         formula:

wherein R⁸, R⁹, R¹⁰, and R¹¹ are each a C_(h)H_(h+1) secondary alkyl group, h is an integer from about 3≦h≦11, and wherein the secondary alkyl group is represented by the formula:

-   -   wherein R¹² and R¹³ are each an alkyl group C_(i)H_(2i+1), and i         is an integer of about 1≦i≦5; and     -   (c3) a combination of (c1) and (c2); and/or

(d) an extreme pressure (EP) additive comprising:

-   -   (d1) an aryl phosphate, an alkyl phosphate, an alkyl amine         phosphite, or an aryl amine phosphite, preferable hindered         phosphite, represented by the general formula:

wherein R¹⁴R¹⁵, R¹⁶, R¹⁷, R¹⁸ and R¹⁹ are each independently a C_(j)H_(2j+1) alkyl group, j is an integer of about 1≦j≦20;

-   -   (d2) a combination of (d1) and a phenol compound represented by         the general formula:

wherein R²⁰, R^(20′), R^(20″), and R^(20′″) are each independently a C_(p)H_(2p+1) normal alkyl group, p is an integer of about 1≦p≦12, wherein R²¹, R^(21′), R^(21″), and R^(21′″) are each independently a phenol group represented by the following formula:

-   -   wherein R²², R²³, and R²⁴ are each independently a C_(o)H_(2o+1)         alkyl group, wherein o is an integer of about 1≦o≦20, and R²³         and R²⁴ are tertiary structures; and/or

(e) a surface fatigue life (SFL) modifier represented by an alkylthiocarbamoyl compound of the following formula:

wherein R²⁵, R²⁶, R²⁷, and R²⁸ are each independently a C_(k)H_(k+1) alkyl group, wherein k is an integer of about 1≦k≦30; R²⁵, R²⁶, R²⁷, and R²⁸ optionally form a ring structure as combined with the nitrogen atom to which they are bonded, wherein (A) consists of a chain of sulfur atoms, S_(n), or the following structure:

S—(CH₂)_(m)—S

Wherein n is an integer of about 1≦n≦10, and m is an integer of about 1≦m≦6.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE shows the relationship between the average traction (friction) coefficient and average load stage for various lubricants. The vertical arrows 11, 21, 31 indicate the average scuffing (scoring) failure load stage (load carrying capacity) of Hatco HXL-7944 Oil 10, Exxon-Mobil Jet Oil II 20; and Formulation #4 30, respectively. A higher scuffing (scoring) failure load stage indicates greater load-carrying capacity of the lubricant.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a multifunctional lubricant composition. One preferred non-limiting embodiment of this multifunctional lubricant composition includes the following: (1) a base stock lubricant (a) in a concentration of about 90% or more by mole, preferably more than about 94% by mole; (2) about 4% or less by mole, preferably about 0.1% to 3% by mole, of friction modifying additive(s) (b); (3) about 4% or less by mole, preferably about 0.1% to 3% by mole, of antiwear additive(s) (c); (4) about 6% or less by mole, preferably about 0.1% to 3% by mole, of extreme pressure additive(s) (d); and about 4% or less by mole, preferably about 0.01% to 1% by mole, of a surface fatigue life modifier(s), all based on the total amount of lubricant. The total amount of additives (b)-(e) should not exceed about 10% by mole, based on the total amount of the lubricant. The present invention contemplates the use of one or more of the additives (b)-(e) with the base stock lubricant (a).

Various types of lubricants, greases, etc., especially synthetic polyol ester (POE) based lubricants, can be used as the lubricating base stock material in this invention.

The lubricant compositions of this invention are prepared by mixing the following components:

(a) a base stock lubricant, which is preferably a synthetic oil (i.e., a synthetic polyol ester (POE) oil);

(b) a friction modifying (FM) additive comprising:

-   -   (b1) a long-chain organic partial ester (i.e., glycerol         mono-oleate (GMO)), having the general formula:

wherein R¹ and R² are each independently a C_(i)H_(2i+1) normal alkyl group, wherein i is an integer of about 7≦i≦15, preferably about 8≦i≦10;

-   -   (b2) a short-chain metallo-organic compound (i.e., molybdenum         dithiocarbamate) represented by the general formula:

wherein X¹ is oxygen and/or sulfur, wherein R³ and R⁴ are each a C_(n)H_(2n+1) alkyl group, n is an integer of about 2≦n≦10, preferably about 4≦n≦6, and m is an integer of about 0≦m≦4; and/or

-   -   (b3) a combination of (b1) and (b2);

(c) an antiwear (AW) additive comprising:

-   -   (c1) an alkyl neutral phosphate or an aryl neutral phosphate         (i.e., tricresyl phosphate (TCP)) represented by the formula:

-   -   wherein the R⁵, R⁶, and R⁷ are each C_(n)H_(2n+1) alkyl groups         of an alkyl neutral phosphate or C₆H₅C_(m)H_(2m+1) aryl groups         of an aryl neutral phosphate, n is an integer of about 2≦n≦10,         preferably about 4≦n≦6, and m is an integer of about 0≦m≦8,         preferably about 1≦m≦5;     -   (c2) a zinc dialkyl dithiophosphate (i.e., Zinc         O,O-dibutylphosphorodithioate) represented by the general         formula:

wherein R⁸, R⁹, R¹⁰, and R¹¹ are each a C_(h)H_(h+1) secondary alkyl group, h is an integer from about 3≦h≦11, preferably about 4≦h≦6, and wherein the secondary alkyl group is represented by the formula:

-   -   wherein R¹² and R¹³ are each an alkyl group C_(i)H_(2i+1), and i         is an integer of about 1≦i≦5, preferably about 1≦i≦3; and/or     -   (c3) a combination of (c1) and (c2); and

(d) an extreme pressure (EP) additive comprising:

-   -   (d1) an aryl phosphate, an alkyl phosphate, an alkyl amine         phosphite, or an aryl amine phosphite, preferably a hindered         phosphate (i.e. Tris-(2,4-di-tertiary-butyl-phenyl)Phosphite)         represented by the general formula:

-   -   -   wherein R¹⁴, R¹⁵, R¹⁶R¹⁷, R¹⁸ and R¹⁹ are each independently             a C_(j)H_(2j+1) alkyl group, j is an integer of about             1≦j≦20, preferably 4≦j≦8;

    -   (d2) a combination of (d1) and a phenol compound (i.e.,         Pentaerythritol         Tetrakis-(methylene-3,5-di-tert-butyl-4-hydroxyhydrocinnamate)         represented by the general formula:

-   -   wherein R²⁰, R^(20′), R^(20″), and R^(20′″) are each         independently a C_(p)H_(2p+1) normal alkyl group, p is an         integer of about 1≦p≦12, preferably about 1≦p≦5, wherein R²¹,         R^(21′), R^(21″), and R^(21′″) are each independently a phenol         group represented by the following formula:

-   -   wherein R²², R²³, and R²⁴ are each independently a C_(o)H_(2o+1)         alkyl group, wherein O is an integer of about 1≦o≦20, preferably         about 2≦o≦10, and R²³ and R²⁴ are tertiary structures; and/or

(e) a surface fatigue life (SFL) modifier represented by an alkylthiocarbamoyl compound (i.e., Tetra-n-butylthiuram) of the following formula:

wherein R²⁵, R²⁶, R²⁷, and R²⁸ are each independently a C_(k)H_(k+1) alkyl group, wherein k is an integer of about 1≦k≦30, preferably about 4≦k≦8; R²⁵, R²⁶, R²⁷, and R²⁸ optionally form a ring structure as combined with the nitrogen atom to which they are bonded, wherein (A) consists of S_(n) (a chain of sulfur atoms) or the following structure:

S—(CH₂)_(m)—S

wherein n is an integer of about 1≦n≦10, and m is an integer of about 1≦m≦6, preferably about 1≦n≦6 and 1≦m≦3.

In embodiments, the base stock lubricant of component (a) is present in a concentration of about 90% or more by mole, preferably about 94% or more by mole, based on the total amount of lubricant.

In embodiments, the friction modifying additive of component (b) is present in a concentration of about 4% or less by mole, preferably from about 0.1% to 3% by mole, based on the total amount of lubricant.

In embodiments, the antiwear additive of component (c) is present in a concentration of about 4% or less by mole, preferably from about 0.1% to about 3% by mole based on the total amount of lubricant.

In embodiments, the extreme pressure additive of component (d) is present in a concentration of about 6% or less by mole, preferably about 0.1% to 3% by mole, based on the total amount of lubricant.

In embodiments, the surface fatigue life modifier of component (e) is present in a concentration of less than about 4% by mole, preferably about 0.01% to 1% by mole, based on the total amount of lubricant.

In embodiments, the total concentration of the four additives (b)-(e) is about 10% or less by mole based on the total amount of lubricant.

The lubricants of the present invention can be used as improved gear oil, bearing oil, sliding surface lubrication oil, chain lubricating oil, and/or engine oil. In a preferred embodiment, various types of lubricants, greases, especially synthetic polyol ester (POE) based lubricants, can be used as the base stock lubricant.

The lubricants of this invention are useful as aviation (aerospace) and/or automotive lubricants. These lubricants improve engine and transmission power generation and throughput, increase system power density and component surface fatigue life, and reduce friction.

These lubricants may also be used as turbine engine and/or transmission oils, and can be designed to meet civil (FAA) and military (DoD) specifications and requirements.

These lubricants may also be used to improve scuffing (scoring) performance of metals and alloys that are commonly used for power transmission components, including but not limited to gears, bearing, spines shafts, springs, and the like. As such, these lubricants decrease the incidence of component and system failure and rejection during customer acceptance test protocols (ATPs). These lubricants also improve pitting fatigue life (surface fatigue life) and reduce the rate of component and system degradation due to wear and other phenomena.

The following formulations and experimental results illustrate some non-limiting embodiments of the novel lubricants of this invention.

Formulation #2

In this embodiment, a multifunctional additive package was added to Exxon-Mobil Jet Oil II (a standard version of MIL-PRF-23699, a 5 cSt gas turbine oil) to create Formulation #2. Formulation #2 contained the following additives:

Additive Mole % Supplier Friction Modifying Glycerol Monooleate 1.0 Crompton Additive Compound (b) Extreme Pressure Tris-(2,4-di-tertiary-butyl- 0.45 Strem Additive phenyl) Phosphite Chemicals Compound (d) Extreme Pressure Pentaerythritol Tetrakis- 0.05 Sigma- Additive (methylene-3,5-di-tert- Aldrich Compound (d) butyl-4- hydroxyhydrocinnamate)

Exxon-Mobil Jet Oil II typically has excellent lubricant performance compared to other brands and versions of MIL-PRF-23699 oil. This multifunctional additive package increased the load carrying capacity (i.e., scuffing performance) of the Exxon-Mobil Jet Oil II about 1.43 times. Additionally, the components that were tested with Formulation #2 had a surface fatigue life of at least about 2.9 times that of the components that were tested with the Exxon-Mobil Jet Oil II alone (unmodified by any additive package of this invention).

Formulation #4

In this embodiment, a multifunctional additive package was added to Hatco HXL-7994 oil to create Formulation #4. Hatco HXL-7994 oil contains an anti-oxidant package and a yellow metal corrosion inhibitor and uses a 5 cSt polyol ester base stock, HXL-1570, having the typical properties noted in Table A below.

TABLE A Properties of HXL-1570 PROPERTY TYPICAL VALUES Viscosity, cSt @ 100° C. 4.95 Viscosity, cSt @ 40° C. 24 Viscosity, cSt @ −40° C. 7500 Viscosity Index 133 Specific Gravity 25/25° C. 0.985 Appearance Clear yellow liquid Hydroxyl, mg KOH/g 2 Density, lbs/usg15.5° C. 8.25 Fire Point 2.82 Evaporation Loss % (6.5 h @ 204° C.) 4 Avg. Molecular Weight 570 Formulation #4 contained the following additives

Product Additive Mole % CAS# Formula Supplier Name Friction Molybdenum, 0.5 71342-89-7 C54H108Mo2N2O2S6 R T MolyVan Modifying bis(ditridecylcarbamodithioato) di-u- Vanderbilt 822/# Additive oxodioxo-di-sulfurized 29150 Compound (b) Antiwear Zinc O,O- 0.5 6990-43-8 C16H36O4P2S4Zn Flexsys Vocol Additive dibutylphosphorodithioate ZBPD Compound (c) Extreme Tris-(2,4-di-tertiary-butyl- 0.5 31570-04-4 C42H63O3P Strem 15-7720 Pressure phenyl) Phosphite Chemicals Additive Compound (d) Surface Tetra-n-butylthiuram 0.4 1634-02-2 C18H36N2S4 R T 40850 Fatigue Vanderbilt Life Modifier Additive Compound (e)

This multifunctional additive package of Formulation #4 increased the load-carrying capacity of the Hatco HXL-7994 oil about 3.94 times, which is superior to conventional oils such as Exxon-Mobil Jet Oil II (a standard version of MIL-PRF-23699, a 5 cSt gas turbine engine oil), which typically has excellent lubricant performance as compared to other brands and versions of MIL-PRF-23699 oil. As can be seen in the FIGURE and Table 1 below, the Hatco HXL-7994 oil 10 had an average scuffing (scoring) failure load stage at about 5.7 (arrow 11), the Exxon-Mobil Jet Oil II 20 had an average scuffing (scoring) failure load stage at about 19.2 (arrow 21), and Formulation #4 30 had an average scuffing (scoring) failure load stage at about 22.5 (arrow 31), which indicates that Formulation #4 has a load carrying capacity about 3.94 times that of the Hatco HXL-7994 Oil, and that Formulation #4 has a load carrying capacity about 1.17 times that of the Exxon-Mobil Jet Oil II.

TABLE 1 Average Micro- Macro- Scuffing scuff scuff (Scoring) (score) (score) Failure Test Lubricant Ball Disc/t.d. Stage Stage Stage UTLCC6 HXL-7944 UTLCC6-9a 9-10a/3.2 4 16 (Base Oil) UTLCC7 HXL-7944 UTLCC6-9b 9-10a/3.1 6 20 (Base Oil) UTLCc8 HXL-7944 UTLCC5-9b 9-10a/3.0 7, 16 17 5.7 (Base Oil) UTLCC16 Formulation #4 UTLCC16-9a 9-10b/2.9 24 UTLCC17 Formulaiton #4 UTLCC16-9b 9-10b/2.8 21 22.5 UTLCC1 Exxon-Mobil SBAD12-9a 9-10a/3.7 25 Jet Oil II UTLCC2 Exxon-Mobil SBAD12-9b 9-10a/3.6 15 Jet Oil II UTLCC3 Exxon-Mobil UTLCC3-9a 9-10a/3.5 24 Jet Oil II UTLCC4 Exxon-Mobil UTLCC3-9b 9-10a/3.4 25 Jet Oil II UTLCC5 Exxon-Mobil UTLCC5-9a 9-10a/3.3 7 15 19.2 Jet Oil II

Experimental Results I. Load-Carrying Capacity (Scuffing Performance)

The load-carrying capacity experimental results for the two Formulations of this invention and the two base oils noted above were obtained using a generally accepted modified variation of the Wedeven Associates, Inc. WAM Load Capacity Test Method (“WAM Test”). The WAM Test is designed to evaluate the load-carrying capacity of lubricants and load bearing surfaces by evaluating the wear, tear, and scuffing thereof over a large temperature range.

Table 2 below gives a summary of the WAM Test conditions that were utilized to test various lubricants of this invention.

TABLE 2 Ball: AISI 9310; Ra: 10-12 μin Disc: AISI 9310; Ra: 6; μin Ball Velocity: 234 in/sec Disc Velocity: 234 in/sec Disc Hardness: 62.5-63.5 HRC Ball Hardness: 62.5-63.5 HRC Rolling Velocity: 158 in/sec Sliding Velocity: 345 in/sec Entraining Velocity: 158 in/sec Velocity Vector Angle (Z): 95° Temperature: Ambient (~22° C.)

For a detailed description of the WAM Test, see WAM High Speed Load Capacity Test Method, SAE Aerospace AIR4978, Revision B, 2002, and U.S. Pat. No. 5,679,883 to Wedeven, both of which are hereby incorporated in full by reference.

High load-carrying oils frequently result in test suspension at load stage 30 without a scuffing event. To differentiate candidate formulations that reach test suspension, tests can be run with a modified test protocol. The modified protocol operates at a lower entraining velocity than the standard test protocol, which reduces the EHD film thickness and increases the test severity by causing greater asperity interaction; essentially operating at a reduced film thickness to surface roughness (h/a) ratio.

The modified test protocol was developed for high load-carrying oils used for aviation gearboxes. These oils include the DOD-PRF-85734 oils for the U.S. Navy and the Def Stan 91-100 oils for the U.K. Ministry of Defense. With the modified test protocol, the highest load-carrying oils currently used in military aircraft experience scuffing failures at load stages that range from approximately 19 to 28.

AISI 9310 Specimen Preparation:

Formulation #4 and the Hatco HXL-7944 oil, and Formulation #2 and the Exxon-Mobil Jet Oil II, were comparatively evaluated for scuffing (scoring) resistance using the modified WAM Test method described above. The test method used ball and disc specimens. The ball specimens were 13/16-inch diameter, and the disc specimens were 4 inches in diameter and ½ inch thick. Material composition, hardness and surface finish were closely controlled. The specimens were fabricated from AISI 9310 steel, a surface-carburizing alloy that is very common for gear applications.

AISI 9310 balls, or “Hard Ground” balls were heat-treated and ground in a ball manufacturing process. The balls were fabricated through the hard grinding stage. The surface finish following this operational stage was between 10-12 micro inch Ra (arithmetic average roughness).

The composition, hardness and surface finish of the specimens are given below:

Disc Specimens Hardness (HRC) Surface Finish (μin. Ra) AISI 9310 63 6 Pyrowear 63 60-61 6 Pyrowear 53 60-61 1-2 superfinished

Scuffing (Scoring) Results:

The scuffing (scoring) results of Formulation #4 as compared to the Hatco HXL-7944 Oil are summarized in Table C, and the results of Formulation #2 as compared to the Exxon-Mobil Jet Oil II are summarized in Table D. Some of these results are also depicted graphically in the FIGURE.

TABLE C Average Micro- Macro- Scuffing Increased scuff scuff (Scoring) Load- (score) (score) Failure Carrying Lubricant Ball Disc/t.d. Stage Stage Stage Capacity HXL-7944 UTLCC6-9a 9-10a/3.2 4 16 HXL-7944 UTLCC6-9b 9-10a/3.1 6 20 HXL-7944 UTLCC5-9b 9-10a/3.0 7, 16 17 5.7 1 Formulation #4 UTLCC16-9a 9-10b/2.9 24 Formulation #4 UTLCC16-9b 9-10b/2.8 21 22.5 3.94

TABLE D Average Micro- Macro- Scuffing Increased scuff scuff (Scoring) Load- (score) (score) Failure Carrying Lubricant Ball Disc/t.d. Stage Stage Stage Capacity Exxon-Mobil Jet Oil II SBAD12-9a 9-10a/3.7 25 Exxon-Mobil Jet Oil II SBAD12-9b 9-10a/3.6 15 Exxon-Mobil Jet Oil II UTLCC3-9a 9-10a/3.5 24 Exxon-Mobil Jet Oil II UTLCC3-9b 9-10a/3.4 25 Exxon-Mobil Jet Oil II UTLCC5-9a 9-10a/3.3 7 15 19.2 1 Formulation #2 UTLCC12-9a 9-10b/3.3 27 Formulation #2 UTLCC12-9b 9-10b/3.2 28 27.5 1.43

The load carrying capacity is indicated by an average scuffing (scoring) failure stage (load stage). Increased performance is observed with higher load stages.

Using this modified WAM Test protocol, it was found that the multifunctional additive package utilized in Formulation #4 increased the load carrying capacity (i.e., scuffing performance) of the Hatco HXL-7944Oil about 3.94 times. As can be seen in the attached FIGURE and Table C, the Hatco HXL-7944 Oil had an average scuffing failure load stage at about 5.7 (arrow 11), and Formulation #4 had an average scuffing failure load stage at about 22.5 (arrow 31), which indicates that Formulation #4 has a load carrying capacity about 3.94 times that of the Hatco HXL-7944 Oil.

Using this modified WAM Test protocol, it was also found that the multifunctional additive package utilized in Formulation #2 increased the load carrying capacity (i.e., scuffing performance) of the Exxon-Mobil Jet Oil II about 1.43 times. As can be seen in the attached FIGURE and Table D, the Exxon-Mobil Jet Oil II had an average scuffing failure load stage at about 19.2 (arrow 21), and Formulation #2 had an average scuffing failure load stage at about 27.5 (not shown on the FIGURE), which indicates that Formulation #2 has a load carrying capacity about 1.43 times that of the Exxon-Mobil Jet Oil II.

II. Surface Fatigue Life Measurement by Spur Gear Testing

Spur gear blanks, having a pitch diameter of 4 inches (100 mm), were fabricated from the Carpenter Technology alloy, Pyrowear alloy 53, in vacuum-induction-melted, vacuum-arc-remelted (VIM/VAR) condition. Following rough machining, gear blanks were given a standard heat treatment and carburization cycle and were finish ground to produce gears that conform to minimum standards of AGMA class 12. The arithmetic average surface roughness of the spur gear involute surfaces that resulted from the final grinding operation was nominally 16 pin. Following final grinding, some gears were afforded an isotropic superfinishing operation to refine the surface finish on the involute surfaces to a nominal arithmetic average value of 2 μin.

Spur-gear tests were performed on a “four-square” test machine, in which two pairs of identical, mated gears are exposed to the same conditions of contact stress, rotational speed, oil-film thickness, and oil temperature. The employed test protocol called for experimental conditions to remain imposed on the spur gears until incipient failure was detected by in situ accelerometers, in which the accelerometer signal amplitude exceeded a predetermined threshold. Visual examination was used to confirm surface failure of the spur-gear involute surface. Specific conditions that were applied for the conducted spur-gear tests included a rotational speed of 3500 min⁻¹, an inlet oil temperature of approximately 115° F. (46° C.), and an oil film thickness of approximately 6 μin (152 nm). Discrete contact stresses of 235 Ksi (1.62 GPa) or 280 Ksi (1.93 GPa) were applied and maintained until surface failure was detected and confirmed. The ball and disc were composed of AISI 9310 and had a surface hardness, using the Rockwell “C” scale (HRC) surface hardness, of Rc 63 (63 HRC).

Results from the spur-gear tests are summarized in Table 3 below. As indicated in Table 3, the average life to surface-fatigue life of as-ground gears lubricated with Formulation #2 at a contact stress of 235 Ksi (1.62 GPa) is a factor of 2.9 times greater than that for as-ground gears lubricated with Exxon-Mobil Jet Oil II. Similarly, the surface-fatigue life of isotropically superfinished (ISF) spur gears lubricated with Formulation #2 at a contact stress of 280 Ksi (1.93 GPa) is a factor of more than 3.3 times greater than that for ISF-processed gears lubricated with Exxon-Mobil Jet Oil II.

TABLE 3 Surface Contact Power Surface Life Surface Roughness Stress Increase Life, N_(f) Increase Condition (μin) Lubricant (Ksi) Factor (×10⁶) Factor As-Ground 16 Exxon-Mobil 235 1.00 16.6 1.0 Jet Oil II Formulation #2 235 1.00 48.3 2.9 ISF- 2 Exxon-Mobil 263 1.25 >61.9 >3.7 Processed Jet Oil II 280 1.42 37.6 2.3 Formulation #2 280 1.42 >55.1 >3.3

While the embodiments described above are directed to lubricants of the polyol ester (POE) type, a skilled artisan would recognize that the compositions apply equally to other lubricant stock compositions including, but not limited to, lubricants comprising grease, mineral (hydrocarbon-based), polyalkylene glycol (PAG), aromatic naphthalene (AN), alkyl benzenes (AB) and polyalphaolefin (PAO) types.

It should therefore be understood that the foregoing description is only illustrative of the present invention. A skilled artisan, without departing from the present invention, can devise various alternatives and modifications. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variations that fall within the scope of the appended claims. 

1. A multifunctional lubricant composition for improving the performance characteristics of a lubricant, said composition comprising: a base stock lubricant; and a friction modifier comprising at least one of a long-chain organic partial ester and a short-chain metallo-organic compound, wherein the long-chain ester has the general formula:

wherein R¹ and R² are each a C_(i)H_(2i+1) alkyl group, wherein i is an integer of about 7≦i≦15; wherein the short-chain metallo-organic compound has the general formula:

wherein X¹ is oxygen or sulfur, wherein R³ and R⁴ are each a C_(n)H_(2n+1) alkyl group, wherein n is an integer of about 2≦n≦10, and m is an integer of about 0≦m≦4.
 2. The composition according to claim 1, wherein the long-chain organic ester is glycerol monooleate.
 3. The composition according to claim 1, wherein the short-chain metallo-organic compound is molybdenum dithiocarbamate.
 4. The composition according to claim 1, further comprising: an antiwear additive comprising at least one of an alkyl neutral phosphate, an aryl neutral phosphate, and a zinc dialkyl dithiophosphate, wherein the alkyl neutral phosphate and the aryl neutral phosphate have the general formula:

wherein the R⁵, R⁶, and R⁷ are each a C_(n)H_(2n+1) alkyl group, wherein the R⁵, R⁶, and R⁷ are each a C₆H₅C_(m)H_(2m+1) aryl group, n is an integer of about 2≦n≦10, m is an integer of about 0≦m≦8; wherein the zinc dialkyl dithiophosphate compound is represented by the general formula:

wherein R⁸, R⁹, R¹⁰, and R¹¹ are each a C_(h)H_(h+1) secondary alkyl group, h is an integer from about 3≦h≦11, wherein the secondary alkyl group is represented by the formula:

wherein R¹² and R¹³ are each an alkyl group C_(i)H_(2i+1), i is an integer of about 1≦i≦5.
 5. A composition according to claim 4, wherein the aryl neutral phosphate is tricresyl phosphate.
 6. The composition according to claim 1, further comprising: an extreme pressure additive comprising at least one of an aryl phosphate, an alkyl phosphate, an alkyl amine phosphite, and an aryl amine phosphite, represented by the general formula:

wherein R¹⁴, R¹⁵, R¹⁶, R¹⁷, R¹⁸ and R¹⁹ are each independently a C_(j)H_(2j+1) alkyl group, j is an integer of about 1≦j≦20;
 7. A composition according to claim 6 further including a phenol compound represented by the general formula:

wherein R²⁰, R^(20′), R^(20″), and R^(20′″) are each independently a C_(p)H_(2p+1) normal alkyl group, p is an integer of about 1≦p≦12, wherein R²¹, R^(21′), R^(21″), and R^(21′″) are each independently a phenol group represented by the following formula:

Wherein R²², R²³, and R²⁴ are each independently a C_(o)H_(2o+1) alkyl group, wherein o is an integer of about 1≦o≦20, R²³ and R²⁴ are tertiary structures.
 8. A composition according to claim 6, wherein the extreme pressure additive comprises a hindered phosphate comprising tris-(2,4-ditertertiarybutylphenyl phosphite).
 9. A composition according to claim 1, further comprising: a surface fatigue life modifier comprising an alkylthiocarbamoyl compound of the following formula:

wherein R²⁵, R²⁶, R²⁷, and R²⁸ are each a C_(k)H_(k+1) alkyl group, wherein k is an integer of about 1≦k≦30; R²⁵, R²⁶, R²⁷, and R²⁸ optionally form a ring structure as combined with the nitrogen atom to which they are bonded, wherein (A) consists of S_(n) (a chain of sulfur atom) or the following structure: S—(CH₂)_(m)—S wherein n is an integer of about 1≦n≦10 and m is an integer of about 1≦m≦6.
 10. The composition according to claim 1, wherein i of the friction modifier is an integer of about 8≦i≦10 and n of the friction modifier is an integer of about 4≦n≦6.
 11. The composition according to claim 4, wherein n of the antiwear additive is an integer of about 4≦n≦6, m of the antiwear additive is an integer of about 1≦m≦5, and h of the antiwear additive is an integer 4≦h≦6.
 12. The composition according to claim 6, wherein j of the extreme pressure additive is an integer of about 4≦j≦8; p of the extreme pressure additive is an integer of about 1≦p≦5; and the composition according to claim 7, where in o of the extreme pressure additive is an integer of about 2≦o≦110.
 13. The composition according to claim 9, wherein k of the surface fatigue life modifier is an integer of about 4≦k≦8.
 14. The composition according to claim 1, wherein the base stock lubricant is present in an amount of about 90% or more by mole based on the total amount of lubricant.
 15. The composition according to claim 1, wherein the base stock lubricant is present in an amount of about 94% or more by mole based on the total about of lubricant.
 16. The composition according to claim 1, wherein the friction modifier is present in an amount of about 4% or less by mole based on the total about of lubricant.
 17. The composition according to claim 1, wherein the friction modifier is present in an amount of about from 0.1% to 3% based on the total amount of lubricant.
 18. The composition according to claim 4, wherein the antiwear additive is present in an amount of about 4% by mole or less based on the total amount of lubricant.
 19. The composition according to claim 4, wherein the antiwear additive is present in an amount of about from 0.1% to 3% by mole based on the total amount of lubricant.
 20. The composition according to claim 6, wherein the extreme pressure additive is present in an amount of about 6% or less by mole based on the total amount of lubricant.
 21. The composition according to claim 6, wherein the extreme pressure additive is present in an amount of about from 0.1% to 3% by mole based on the total amount of lubricant.
 22. The composition according to claim 9, wherein the surface fatigue life modifier is present in an amount of about 4% or less by mole based on the total amount of lubricant.
 23. The composition according to claim 9, wherein the surface fatigue life modifier is present in an amount of about from 0.01% to 1% by mole based on the total amount of lubricant.
 24. The composition according to claim 4, further comprising an extreme pressure additive comprising at least one of an aryl phosphate, an alkyl phosphate, an alkyl amine phosphite, and an aryl amine phosphite, represented by the general formula:

wherein R¹⁴, R¹⁵, R¹⁶, R¹⁷, R¹⁸ and R¹⁹ are each independently a C_(j)H_(2j+1) alkyl group, j is an integer of about 1≦j≦20;
 25. A composition according to claim 24 further including a phenol compound represented by the general formula:

Wherein R²⁰, R^(20′), R^(20″), and R^(20′″) are each independently a C_(p)H_(2p+1) normal alkyl group, p is an integer of about 1≦p≦12, wherein R²¹, R^(21′), R^(21″), and R^(21′″) are each independently a phenol group represented by the

following formula: wherein R²², R²³, and R²⁴ are each independently a C_(o)H_(2o+1) alkyl group, wherein o is an integer of about 1≦o≦20, R²³ and R²⁴ are tertiary structures.
 26. A composition according to claim 4, further comprising a surface fatigue life modifier comprising an alkylthiocarbamoyl compound of the following formula:

wherein R²⁵, R²⁶R²⁷, and R²⁸ are each a C_(k)H_(k+1) alkyl group, wherein k is an integer of about 1≦k≦30; R²⁵, R²⁶, R²⁷, and R²⁸ optionally form a ring structure as combined with the nitrogen atom to which they are bonded, wherein (A) consists of S_(n) (a chain of sulfur atoms) or the following structure: S—(CH₂)_(m)—S wherein n is an integer of about 1≦n≦10 and m is an integer of about 1≦m≦6.
 27. The composition according to claim 9, further comprising further comprising: an extreme pressure additive comprising at least one of an aryl phosphate, an alkyl phosphate, an alkyl amine phosphite, and an aryl amine phosphite, represented by the general formula:

wherein R¹⁴, R¹⁵, R¹⁶, R¹⁷, R¹⁸ and R¹⁹ are each independently a C_(j)H_(2j+1) alkyl group, j is an integer of about 1≦j≦20;
 28. A composition according to claim 27 further including a phenol compound represented by the general formula:

wherein R²⁰, R^(20′), R^(20″), and R^(20′″) are each independently a C_(p)H_(2p+1) normal alkyl group, p is an integer of about 1≦p≦12, wherein R²¹, R^(21′), R^(21″), and R^(21′″) are each independently a phenol group represented by the following formula:

Wherein R²², R²³, and R²⁴ are each independently a C_(o)H_(2o+1) alkyl group, wherein o is an integer of about 1≦o≦20, R²³ and R²⁴ are tertiary structures.
 29. A multifunctional lubricant composition comprising: (a) a base stock lubricant; and at least one of (b), (c), (d) and (e), (b) a friction modifying (FM) additive comprising: (b1) a long-chain organic partial ester having the general formula:

wherein R¹ and R² are each independently a C_(i)H_(2i+1) normal alkyl group, wherein i is an integer of about 7≦i≦15; (b2) a short chain metallo-organic compound represented by the general formula:

Wherein X¹ is oxygen and/or sulfur, wherein R³ and R⁴ are each a C_(n)H_(2n+1) alkyl group, n is an integer of about 2≦n≦10, and m is an integer of about 0≦m≦4; and/or (b3) a combination of (b1) and (b2); (c) an antiwear (AW) additive comprising: (c1) an alkyl neutral phosphate or an aryl neutral phosphate represented by the formula:

wherein the R⁵, R⁶, and R⁷ are each C_(n)H_(2n+1) alkyl groups of an alkyl neutral phosphate or C₆H₅C_(m)H_(2m+1) aryl groups of an aryl neutral phosphate, n is an integer of about 2≦n≦10, and m is an integer of about 0≦m≦8; (c2) a zinc dialkyl dithiophosphate represented by the general formula:

wherein R, R⁹, R¹⁰, and R¹¹ are each a C_(h)H_(h+1) secondary alkyl group, h is an integer from about 3≦h≦11, and wherein the secondary alkyl group is represented by the formula:

wherein R¹² and R¹³ are each an alkyl group C_(i)H_(2i+1), and i is an integer of about 1≦i≦5; and/or (c3) a combination of (c1) and (c2); and (d) an extreme pressure (EP) additive comprising: (d1) an aryl phosphate, an alkyl phosphate, an alkyl amine phosphite, or an aryl amine phosphite represented by the general formula:

wherein R¹⁴R¹⁵, R¹⁶, R¹⁷, R¹⁸ and R¹⁹ are each independently a C_(j)H_(2j+1) alkyl group, j is an integer of about 1≦j≦20; (d2) a combination of (d1) and a phenol compound represented by the general formula:

wherein R²⁰, R^(20′), R^(20″), and R^(20′″) are each independently a C_(p)H_(2p+1) normal alkyl group, p is an integer of about 1≦p≦12, wherein R²¹, R^(21′), R^(21″), and R^(21′″) are each independently a phenol group represented by the following formula:

wherein R²², R²³, and R²⁴ are each independently a C_(o)H_(2o+1) alkyl group, wherein O is an integer of about 1<O<20, and R²³ and R²⁴ are tertiary structures; and (e) a surface fatigue life (SFL) modifier represented by an alkylthiocarbamoyl compound of the following formula:

wherein R²⁵R²⁶, R²⁷ and R²⁸ are each a C_(k)H_(k+1) alkyl group, wherein k is an integer of about 1≦k≦30; R²⁵, R²⁶, R²⁷, and R²⁸ optionally form a ring structure as combined with the nitrogen atom to which they are bonded, wherein (A) consists of S_(n) (a chain of sulfur atoms) or the following structure: S—(CH₂)_(m)—S wherein n is an integer of about 1≦n≦10, and m is an integer of about 1≦m≦6. 